Brushless synchronous motor main motor rotor with built-in distributed magnetic barriers

Abstract

The application relates to a brushless synchronous motor rotor with built-in distributed magnetic barriers, which comprises a rotor core, an excitation winding and a damping winding, the rotor core is provided with a plurality of magnetic poles, the magnetic poles comprise pole bodies and pole shoes, the pole shoe surfaces are provided with damping grooves, the excitation winding is wound on the pole bodies, and the damping winding is arranged in the damping grooves; the rotor core pole shoes are provided with rotor magnetic barriers, the rotor magnetic barriers comprise cross-axis magnetic barriers and direct-axis magnetic barriers, the cross-axis magnetic barriers are arranged along the radial direction of the rotor core and are connected with the damping grooves, and the direct-axis magnetic barriers are arranged on both sides of the pole shoes. The application is innovative in that the distributed magnetic barriers are arranged in the brushless synchronous motor rotor for the first time to improve the output power quality. The basic principle is that by arranging the magnetic barriers at key positions of the rotor, the cross-axis and direct-axis magnetic resistances are increased, the negative sequence reactance is reduced, the generator anti-unbalanced load capacity is improved under the unbalanced load working condition, and the total harmonic content of the generator output voltage is reduced under the balanced load working condition. Since the magnetic barrier medium density is smaller than the core material density, the weight of the generator with the built-in rotor magnetic barriers is reduced, and the power density is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to a brushless synchronous motor main motor rotor with built-in distributed magnetic barriers, belonging to the technical field of brushless synchronous motors. Since the brushless synchronous motor main motor is an electrically excited synchronous motor structure, the present application is also applicable to various application scenarios of electrically excited synchronous generators to improve the output power quality. BACKGROUND

[0002] The aviation three-stage brushless synchronous motor solves the problem of arc extinction of the brush slip ring at high altitude and high speed of the aircraft motor due to its brushless feature, and has an independent permanent magnet excitation source and a controllable electric excitation excitation source, greatly ensuring the high reliability of the aviation power supply system. Compared with high-power-density permanent magnet motors, the simplicity and reliability of the body and control layer and the technical maturity of the system design are the main advantages of the three-stage brushless synchronous motor, which is the key to being widely used in aircraft main power supply systems.

[0003] The variable frequency alternating current power supply system is one of the important directions of the development of the main power supply system of the more electric aircraft, has the characteristics of improving the efficiency of the main power supply system, optimizing the aircraft engine system and being compatible with most constant frequency alternating current loads, while ensuring low technical iteration cost, greatly improving the capacity of the aircraft main power supply system.

[0004] However, the application of the three-stage brushless synchronous motor in the variable frequency alternating current power supply system will face many challenges, the most prominent of which is the problem of poor power quality of the generator under high frequency conditions. When the variable frequency alternating current generator speed increases, the output voltage frequency increases, resulting in increased reactance, increasing the three-phase asymmetry of the motor load, and increasing the unbalance degree of the motor output voltage; during the frequency rise process, the harmonic content of the output voltage also shows an increasing trend; both of which lead to a decrease in output power quality. As the frequency increases, the alternating current copper loss in the generator armature winding increases, resulting in a sharp increase in stator temperature rise, which is prone to inter-turn short circuit and other motor operation accidents.

[0005] To improve the power quality of the generator under high frequency conditions, a new method for improving the output power quality of the three-stage brushless synchronous motor is proposed - the rotor built-in magnetic barrier, based on which a brushless synchronous motor main motor rotor with built-in distributed magnetic barriers is invented. SUMMARY

[0006] The present application provides a brushless synchronous motor main motor rotor with built-in distributed magnetic barriers to reduce the size of negative sequence magnetic flux and reduce negative sequence reactance, to solve the technical problem of high-quality power supply of the aviation variable frequency alternating current generator under high frequency conditions.

[0007] In order to achieve the above object, the technical scheme of the application is as follows: a brushless synchronous motor rotor with built-in distributed magnetic barriers, comprising a rotor core, an excitation winding and a damping winding, the rotor core is provided with a plurality of magnetic poles, the magnetic pole comprises a pole body and a pole shoe, the pole shoe is provided with a damping slot, the excitation winding is wound on the pole body, and the damping winding is arranged in the damping slot; the pole shoe of the rotor core is provided with a rotor magnetic barrier, the rotor magnetic barrier comprises a quadrature-axis magnetic barrier and a direct-axis magnetic barrier, the quadrature-axis magnetic barrier is arranged along the radial direction of the damping winding and connected with the damping slot, and the direct-axis magnetic barrier is arranged on both sides of the pole shoe and arranged along the tangential direction of the rotor.

[0008] Further design of the above technical scheme is as follows: a plurality of quadrature-axis magnetic barriers are respectively connected with a damping slot, and a direct-axis magnetic barrier is arranged on both sides of the pole shoe.

[0009] The rotor magnetic barrier is a rectangular notch filled with air, and the rectangular notch penetrates the rotor core.

[0010] The edge of the rectangular notch of the rotor magnetic barrier is chamfered.

[0011] The rotor core is provided with damping end plates at both ends, the two damping end plates axially cover both ends of the rotor core, and the damping windings are short-circuited.

[0012] The rotor core is provided with a rivet slot at the center of the magnetic pole, the damping end plate is provided with a through hole at the corresponding position, and the two damping end plates are connected to the rotor core by passing through the through hole of one damping end plate, the rivet slot and the through hole of the other damping end plate in sequence through a rivet.

[0013] The rotor core is provided with a damping slot at the center of the magnetic pole, the damping slot is connected with a quadrature-axis magnetic barrier, and the quadrature-axis magnetic barrier is in communication with the corresponding rivet slot.

[0014] A plurality of weight-reducing holes are arranged on the rotor core in the circumferential direction.

[0015] The beneficial effects of the application are as follows:

[0016] By arranging the rotor magnetic barrier on the rotor core, the quadrature and direct-axis magnetic resistance can be increased, the negative sequence magnetic flux can be reduced, the negative sequence reactance can be reduced, and the motor anti-unbalanced load capacity can be effectively improved; the rotor magnetic barrier can suppress the quadrature-axis armature reaction, optimize the radial air gap magnetic density sine degree, reduce the output voltage harmonic content, and further reduce the motor core loss; the tangential air gap magnetic density variation rate is reduced, and the stator armature winding AC copper loss is reduced.

[0017] Compared with the traditional three-stage brushless synchronous motor rotor, the motor rotor of the application is provided with an air gap magnetic barrier, which requires less amount of core material, has lighter motor weight and higher power density on the basis of ensuring high power quality generation. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Structure diagram of main motor rotor of brushless synchronous motor of embodiment one of the present application;

[0019] Figure 2 Structure diagram of damping winding and damping end plate of motor rotor of embodiment one;

[0020] Figure 3 Structure diagram of motor rotor iron core with built-in direct and quadrature axis magnetic barriers of embodiment one;

[0021] Figure 4 Positioning diagram of direct and quadrature axis magnetic barriers of motor rotor of embodiment one;

[0022] Figure 5 Key parameter diagram of rotor magnetic barrier;

[0023] Figure 6 Equivalent magnetic circuit principle diagram after built-in magnetic barrier of rotor;

[0024] Figure 7 Diagram of armature reaction direct axis main magnetic circuit of armature winding after setting magnetic barrier;

[0025] Figure 8 Diagram of armature reaction direct axis main magnetic circuit of armature winding without setting magnetic barrier;

[0026] Figure 9 Diagram of armature reaction quadrature axis main magnetic circuit of armature winding after setting magnetic barrier;

[0027] Figure 10 Diagram of armature reaction quadrature axis main magnetic circuit of armature winding without setting magnetic barrier;

[0028] Figure 11 Positioning diagram of direct and quadrature axis magnetic barriers of motor rotor of embodiment two;

[0029] Figure 12 Comparison diagram of output voltage harmonic content when rated load power factor is 0.75 before and after built-in magnetic barrier of rotor;

[0030] Figure 13 Comparison diagram of output voltage harmonic content when rated load power factor is 1.0 before and after built-in magnetic barrier of rotor;

[0031] Figure 14 Comparison diagram of output voltage unbalance degree under typical unbalanced load working condition before and after built-in magnetic barrier of rotor;

[0032] Figure 15 Comparison diagram of phase shift under typical unbalanced load working condition before and after built-in magnetic barrier of rotor.

[0033] In the figure, 1-damping winding, 2-rivet, 3-excitation winding, 4-damping end plate, 5-rotor core, 51-pole shoe, 52-damping slot, 53-rivet slot, 6-direct axis magnetic barrier, 7-quadrature axis magnetic barrier, 8-weight reduction hole. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] like Figure 1 As shown in this embodiment, a main motor rotor of a brushless synchronous motor with built-in distributed magnetic barriers includes a rotor core 5, an excitation winding 3, and a damping winding 1. The rotor core 5 has eight magnetic poles evenly distributed on it. The material is a high-saturation magnetic material 1J22, which is impregnated with varnish and then stacked by rotor laminations. The maximum magnetic flux density is 2.4T. The magnetic pole includes a pole body and a pole shoe 51. Each pole shoe 51 has five parallel damping grooves 52 on its surface. The excitation winding 3 is wound around the pole body and is used for motor excitation. The excitation winding 3 is a flat wire structure made of pure copper. After impregnation with varnish, it is wound in a single turn around the rotor core pole body. The excitation windings 3 between the pole bodies are connected in series.

[0037] The damping winding 1 has five windings per pole, arranged tangentially in parallel within the damping slot 51, and is made of copper. Figure 2 As shown, the rotor core 5 has damping end plates 4 at both ends, and the two damping end plates 4 axially cover the two ends of the rotor core 5 and short-circuit the damping winding 1; the structure of the damping end plates 4 is consistent with the lamination of the rotor core 5, and the material is copper.

[0038] The rotor core 5 has a rivet groove 53 along the axial direction at the center of the magnetic pole shoe, and the damping end plate 4 has a through hole at the corresponding position. The two damping end plates 4 are connected to the rotor core 5 by rivets 2 passing through the through hole, rivet groove 53 and through hole of one damping end plate 4 in sequence. The rivet 2 has the same structure as the damping winding 1 and is used to connect the two damping end plates to the rotor core to fix the damping end plates. It is set on the central axis of the pole body, and each pole body is connected by one rivet 2.

[0039] Combination Figure 3 As shown, in this embodiment, rotor magnetic barriers are provided on the pole shoes 51 of the rotor core 5. The rotor magnetic barriers include quadrature-axis magnetic barriers 7 and direct-axis magnetic barriers 6. Figure 4As shown, three quadrature axis magnetic barriers 7 and two direct axis magnetic barriers 6 are arranged on each magnetic pole, the three quadrature axis magnetic barriers 7 are arranged along the radial direction of the damping winding 1 and are connected with the middle three damping slots 52 of the magnetic pole respectively, for hindering the quadrature axis negative sequence magnetic flux and the leakage magnetic flux of the damping winding, and for inhibiting the quadrature axis armature reaction, the two direct axis magnetic barriers 6 are arranged on the two sides of the corresponding pole shoe and are arranged along the tangential direction of the rotor, for hindering the direct axis negative sequence magnetic flux and the quadrature axis negative sequence magnetic flux, and for inhibiting the direct and quadrature axis armature reactions.

[0040] In the embodiment, the rotor magnetic barrier is a rectangular slot filled with air, which penetrates the rotor core 5 and the edges are chamfered.

[0041] In the embodiment, a plurality of weight-reducing holes 8 are arranged on the rotor core in the circumferential direction, further reducing the weight of the rotor.

[0042] In the embodiment, a damping slot 52 is arranged at the center of the magnetic pole of the rotor core, the damping slot 52 is connected with a quadrature axis magnetic barrier 7, the quadrature axis magnetic barrier 7 is communicated with a rivet slot 53, forming a composite slot structure.

[0043] The magnetic barrier is generally used in the permanent magnet motor to increase the salient pole ratio to increase the torque, but the magnetic barrier arranged in the embodiment is used in the electrically excited brushless synchronous motor, by arranging the quadrature axis magnetic barrier 7 and the direct axis magnetic barrier 6 at the above-mentioned positions, the direct and quadrature axis magnetic resistances can be increased, the negative sequence armature reaction magnetic flux and the leakage magnetic flux of the damping winding are inhibited, and the size of the negative sequence reactance is reduced, so as to improve the ability of the motor to resist unbalanced load and reduce the total harmonic content of the voltage.

[0044] The mechanism of the magnetic barrier and the calculation process of the direct and quadrature axis reactance of the armature reaction are as follows:

[0045] Assumptions: 1. The current in the armature slot part is concentrated on the slot center line; 2. The influence of the slot opening is taken into account by the air gap coefficient.

[0046] Figure 5 The key parameters of the magnetic barrier are marked, wherein l ri is the radial length of the magnetic barrier, l ti is the tangential length of the magnetic barrier. When l ri > l ti , the magnetic barrier is a quadrature axis main magnetic barrier, and when l ri < l ti , the magnetic barrier is a direct axis main magnetic barrier.

[0047] Figure 6 It is an equivalent magnetic circuit diagram after the rotor built-in magnetic barrier, according to Figure 6 a mathematical model of the magnetic barrier is established:

[0048]

[0049] In the formula, μ iLet μ0 be the permeability of a single magnetic barrier after a radial length infinitesimal element, μ0 be the permeability of air, S be the cross-sectional area of ​​the magnetic barrier, and δ be the length of the magnetic barrier l. z This is the axial length of the rotor core.

[0050]

[0051] In the formula, μ m C represents the series permeability of distributed air gap magnetic barriers, where C is the number of distributed air gap magnetic barriers connected in series.

[0052]

[0053] In the formula, μ am The radial length of a single air gap magnetic barrier is l r Distributed magnetic barrier series permeability at that time.

[0054]

[0055] In the formula, μ Fm The radial length of a single iron core magnetic barrier is (l psh -l r Distributed magnetic barrier series magnetic permeability at that time.

[0056]

[0057] In the formula, μ s The rotor has a built-in distributed magnetic barrier with total magnetic permeability.

[0058] When direct-axis negative-sequence armature reaction occurs, the direct-axis magnetic circuit of the negative-sequence armature reaction is as follows: Figure 7 As shown, at this time C=2, i=2, the negative-sequence armature reaction direct-axis magnetic barrier permeability is:

[0059]

[0060] When negative-sequence armature reaction occurs, the negative-sequence armature reaction cross-axis magnetic circuit is as follows: Figure 9 As shown, at this time C=7, i=1, and the negative-sequence armature reaction cross-axis magnetic barrier permeability is:

[0061]

[0062] The negative-sequence armature reaction cross-axis and direct-axis reactances are:

[0063]

[0064]

[0065] From equation (1.5), it can be seen that as the number of magnetic barriers C increases, the tangential length l of the magnetic barriers increases. ti Increase the radial length l of the magnetic barrier riIncreasing the value of the rotor can reduce the total magnetic permeability μ of the rotor's internal distributed magnetic barrier. s Based on this, and combining equations (1.8) and (1.9), it can be seen that the increase of the above-mentioned key parameters of the magnetic barrier can lead to the generator's X... d X q Decrease.

[0066] Based on the above derivation, referring to... Figure 4 As shown, by creating direct-axis magnetic barriers 6 with their length direction in the tangential direction of the rotor on both sides inside the rotor pole shoe 51, the air gap length in the direction of direct-axis negative sequence magnetic flux can be effectively increased, such as... Figure 7 As shown, compared to Figure 8 The rotor shown, without a direct-axis magnetic barrier, can increase the quadrature-direct-axis magnetic reluctance, suppress negative-sequence quadrature-direct-axis armature reaction, and reduce the negative-sequence armature reaction reactance. (Refer to...) Figure 4 As shown, in this embodiment, by providing a quadrature-axis magnetic barrier 7 connected to the damping groove 52 along the radial direction of the rotor core 4 inside the rotor, the length of the air gap in the quadrature-axis negative sequence magnetic flux direction can be effectively increased, thereby increasing the quadrature-axis magnetic reluctance. Figure 9 As shown, compared to Figure 10 The rotor shown without cross-axis magnetic barriers can suppress cross-axis armature reaction and reduce cross-axis armature reaction flux.

[0067] To verify the changes in the total harmonic content of the generator output voltage and its ability to resist unbalanced loads after the rotor incorporates magnetic barriers, the finite element method was used to simulate and compare the total harmonic content of the output voltage and its ability to resist unbalanced loads before and after the rotor incorporates magnetic barriers.

[0068] Reference Figure 12 and Figure 13 At this point, the generator is operating under rated load conditions. When the load power factor is 0.75, the total harmonic distortion (THD) of the output voltage of the generator with built-in rotor magnetic barriers decreases from 1.425% to 0.724%. When the load power factor is 1.0, the THD of the output voltage decreases from 1.204% to 1.071%. From the above comparison, it can be seen that under steady-state balanced load conditions, the THD of the output voltage of the generator with built-in rotor magnetic barriers is lower than that of the generator without rotor magnetic barriers.

[0069] Reference Figure 14 and Figure 15 The generator operates under typical unbalanced load conditions with a load power factor of 1.0. Specifically, a 1 / 6 unbalanced load means phase A carries 1 / 6 of the rated load, while phases B and C are unloaded; a 1 / 3 unbalanced load means phase A carries 1 / 3 of the rated load, while phases B and C are unloaded; and a 2 / 3 unbalanced load means phase A carries 2 / 3 of the rated load, while phases B and C are unloaded. The generator's ability to withstand unbalanced loads is characterized by the voltage unbalance degree ΔU and phase shift ΔP. Under the same load conditions, the smaller ΔU and ΔP are, the stronger the generator's ability to withstand unbalanced loads.

[0070]

[0071] ΔP = [P - 120°] max (1.11)

[0072] wherein U is an arbitrary phase voltage, U avg is the average value of three-phase voltage, and P is the included angle of any two phases.

[0073] Referring to Figure 14 , Figure 15 and Table 1, it can be seen that the greater the unbalanced load of the generator, the greater the output voltage unbalance and phase shift of the generator; after the built-in magnetic barrier of the rotor is provided, the output voltage unbalance and phase shift under each typical unbalanced load condition are reduced, further verifying that the anti-unbalanced load capacity of the generator with the built-in magnetic barrier of the rotor is improved.

[0074] Table 1 is the size of the output voltage unbalance and phase shift under the typical unbalanced load condition.

[0075] Table 1 is the size of the output voltage unbalance and phase shift under the typical unbalanced load condition.

[0076]

[0077] In summary, the embodiment effectively reduces negative sequence cross-axis armature reaction reactance X d , X q and leakage reactance X σ of the damping winding by opening the rotor cross-axis and direct-axis magnetic barrier in the direction of the negative sequence cross-axis armature reaction magnetic flux, improves the anti-unbalanced load capacity of the generator, reduces the total harmonic content of the output voltage, further reduces the iron loss and AC copper loss, improves various output characteristics of the motor, and improves the output power quality of the generator as a whole. Since the magnetic barrier medium is air, the power density of the generator is also improved.

[0078] Embodiment Two

[0079] The main motor rotor structure of the brushless synchronous motor with the built-in distributed magnetic barrier of the embodiment is basically the same as that of Embodiment One, and the difference is that, as shown in Figure 11 , the direct-axis magnetic barrier 6 is in the shape of a water droplet, and the width of one end close to the pole shoes 51 is relatively narrow; the cross-axis magnetic barrier 7 is also in the shape of a water droplet, and the width of one end close to the damping slot 52 is relatively wide, and the width does not exceed the diameter of the damping slot, and the cross-axis magnetic barrier 7 is not connected with the damping slot 52, so as not to affect the structure of the damping winding.

[0080] The embodiment can effectively reduce negative sequence cross-axis armature reaction reactance and damping winding leakage reactance by opening rotor cross-axis magnetic barriers, and compared with the rectangular chamfer magnetic barriers in the first embodiment, the water drop type magnetic barriers in the embodiment reduce the notch area and are more stable in structure under the condition of the same output power quality effect.

[0081] The technical solutions of the present application are not limited to the above embodiments, and any technical solution obtained by equivalent replacement falls within the scope of the present application.

Claims

1. A brushless synchronous motor main motor rotor with built-in distributed magnetic barrier, comprising a rotor core, an excitation winding and a damping winding, a plurality of magnetic poles are arranged on the rotor core, the magnetic poles comprise a pole body and a pole shoe, a damping slot is arranged on the surface of the pole shoe, the excitation winding is wound on the pole body, and the damping winding is arranged in the damping slot; characterized in that: The rotor core is provided with rotor magnetic barriers on the pole shoe, the rotor magnetic barriers include cross-axis magnetic barriers and direct-axis magnetic barriers, the cross-axis magnetic barriers are arranged along the radial direction of the damping winding and connected with the damping slot, and the direct-axis magnetic barriers are arranged on both sides of the pole shoe and along the tangential direction of the rotor; ​ The rotor core is provided with rivet slots at the center of the magnetic pole, the damping end plates are provided with through holes at the corresponding positions, and the two damping end plates are connected to the rotor core by the rivet which passes through the through hole of one damping end plate, the rivet slot and the through hole of the other damping end plate in sequence. The rotor core is provided with a damping slot at the center of the magnetic pole, the damping slot is connected with a cross-axis magnetic barrier in correspondence, and the cross-axis magnetic barrier is communicated with the corresponding rivet slot.

2. The brushless synchronous motor main motor rotor with built-in distributed magnetic barriers according to claim 1, characterized in that: The cross-axis magnetic barriers and the direct-axis magnetic barriers are provided with a plurality of magnetic barriers, the plurality of cross-axis magnetic barriers are connected with a damping slot respectively, and the pole shoe is provided with a direct-axis magnetic barrier on both sides in correspondence.

3. The brushless synchronous motor main motor rotor with built-in distributed magnetic barriers according to claim 2, characterized in that: The rotor magnetic barrier is a hollow rectangular slot, and the rectangular slot penetrates the rotor core.

4. The brushless synchronous motor main motor rotor with built-in distributed magnetic barriers according to claim 3, characterized in that: The edge of the rectangular slot of the rotor magnetic barrier is rounded to ensure the strength of the rotor pole shoe.

5. The brushless synchronous motor main motor rotor with built-in distributed magnetic barriers according to claim 4, characterized in that: The rotor core is provided with damping end plates at both ends, the two damping end plates are axially covered on both ends of the rotor core, and the damping windings are short-circuited.

Images